Sliding-Induced Rehydration in Hydrogels for Restoring Lubrication and Anticreeping Capability
Yunlei Zhang1, Carmine Putignano2,3, Changmin Qi1,4
1State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
The Journal of Physical Chemistry Letters
|November 5, 2024
Summary
Tribological rehydration in hydrogels mimics cartilage’s self-lubrication. Specific velocities restore hydration, enhancing load-bearing capacity and lubrication by counteracting fluid exudation.
Area of Science:
- Biomaterials Science
- Tribology
- Hydrogel Mechanics
Background:
- Cartilage exhibits a sliding-induced rehydration phenomenon for lubrication under normal loading.
- Hydrogels, similar to cartilage, possess tribological rehydration properties that can be mimicked.
- Understanding these properties is crucial for applications requiring sustained lubrication and load-bearing capacity.
Purpose of the Study:
- To investigate and mimic the tribological rehydration phenomenon observed in cartilage within hydrogel systems.
- To explore the influence of sliding velocity, applied load, and hydrogel network structure on rehydration.
- To determine the optimal conditions for restoring hydration lubrication and overcoming creeping in hydrogels.
Main Methods:
- Experimental investigation of hydrogel tribology under varying loads and sliding velocities.
- Analysis of fluid exudation and rehydration inflow dynamics.
- Correlation of hydrogel network structure with tribological rehydration performance.
Main Results:
- Tribological rehydration in hydrogels is achievable within a specific velocity range, dependent on load and network structure.
- A critical velocity in the mixed lubrication regime generates hydrodynamic pressure, driving rehydration inflow.
- Insufficient inflow occurs at low velocities (boundary lubrication), while the wedge effect diminishes at high velocities (hydrodynamic lubrication).
Conclusions:
- Tribological rehydration offers a novel strategy for enhancing hydrogel lubrication and load-bearing capacity.
- The phenomenon is governed by hydrodynamic effects and is sensitive to operating conditions and material properties.
- This approach holds promise for improving the performance and longevity of hydrogel-based materials.
Related Concept Videos
01:07Cohesion
Cohesion is the attraction between molecules of the same type, such as water molecules. Water molecules have an overall neutral charge but are polar molecule. An oxygen atom in one water molecule has a partial negative charge that can bind to a hydrogen atom with a partial positive charge in a second water molecule, forming a hydrogen bond. Each water molecule can form up to four hydrogen bonds with other water molecules. Hydrogen bonds are responsible for water's cohesive nature.
On a surface,...
On a surface,...
01:57Adaptations that Reduce Water Loss
Though evaporation from plant leaves drives transpiration, it also results in loss of water. Because water is critical for photosynthetic reactions and other cellular processes, evolutionary pressures on plants in different environments have driven the acquisition of adaptations that reduce water loss.
02:57Surface Tension, Capillary Action, and Viscosity
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
01:06Coagulation
Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
01:26Regulation of Water Output
The human body predominantly expels water through the urinary system. On average, an individual generates around 1.5 liters of urine each day. This amount can fluctuate based on how well a person is hydrated, but a critical minimum quantity of urine must be produced to ensure the body's proper functioning. Daily, the kidneys remove 600 to 1200 milliosmoles of dissolved substances, effectively excreting excess minerals and water-soluble toxins such as creatinine, urea, and uric acid from the...
01:22Waterproofing and Anti-Bacterial Admixtures in Concrete
Concrete's susceptibility to water absorption is due to the capillary action within the pores of its hydrated cement paste. This action draws water in, creating the need for waterproofing admixtures to prevent such penetration. The efficacy of these admixtures is contingent upon the water pressure, with variations arising from different conditions such as rain, capillary rise, or hydrostatic pressure in structures intended to hold water.
Waterproofing admixtures render concrete hydrophobic,...
Waterproofing admixtures render concrete hydrophobic,...